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Mogami 3080...Microphonic?!
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effitall
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31st October 2010
Old 31st October 2010
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Mogami 3080...Microphonic?!

I've long thought that the AES/EBU digital cables would be quite good for not only digital interconnects, but also mic/line runs. Today I was wiring up some Mogami 3080 and after getting a few made decided to test them out. Upon plugging them in I discovered that the cable is extremely microphonic. Shaking the cable, laying it across your knee and slapping it, even sliding your hand down the cable creates microphonics that are audible.

I first thought that maybe I was just making the cables wrong...Initially I was cutting back the wire shield and only using the drain, but making one with the drain and shield tied together yields the same results. Microphonic cable. With as many people using this stuff, I'm surprised I can't find any mention of it (specifically) being microphonic. Am I missing something?!

Thanks,

James
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31st October 2010
Old 31st October 2010
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Quote:
Originally Posted by effitall View Post
I've long thought that the AES/EBU digital cables would be quite good for not only digital interconnects, but also mic/line runs. Today I was wiring up some Mogami 3080 and after getting a few made decided to test them out. Upon plugging them in I discovered that the cable is extremely microphonic. Shaking the cable, laying it across your knee and slapping it, even sliding your hand down the cable creates microphonics that are audible.

I first thought that maybe I was just making the cables wrong...Initially I was cutting back the wire shield and only using the drain, but making one with the drain and shield tied together yields the same results. Microphonic cable. With as many people using this stuff, I'm surprised I can't find any mention of it (specifically) being microphonic. Am I missing something?!

Thanks,

James
Did you try this with a mic connected? Better, solder a 150 ohm resistor across Pin 2 and 3 of an XLR-M, and use that instead of the mic. Almost every cable is microphonic with no termination/source.

Jim
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effitall
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31st October 2010
Old 31st October 2010
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It was terminated with a microphone. Tried a couple of different ones, both dynamics and both showed the cable to have the same issue. I've got some ProCo and Whirlwind cables that don't act up under the same circumstances. It's just kind of surprising to me. I can't imagine this susceptibility to handling as being good in a digital interconnect.

James
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31st October 2010
Old 31st October 2010
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Are you using an AES type cable for audio? Why? Cables are made in specific types for specific uses. This cable may be made to have low capacitance, and therefore not be suitable for audio. Mogami make good cable and know their business. You obviously don't.
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31st October 2010
Old 31st October 2010
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Mogami 3080...Microphonic?!

Quote:
Originally Posted by Radardoug
Are you using an AES type cable for audio? Why? . Mogami make good cable and know their business. You obviously don't.
Wow. Kind of harsh, no?

But his point about proper application of cable is correct. The critical characteristic for AES/EBU digital cable is specific impedence and uniformity. With the frequencies involved, signal reflections due to impedence variatiins are a real possibility, and can result in errors. Microphonics aren't really a concern at all in that application, so the cable probably isn't designed to minimize that effect. I guess that's not a surprise, whenyou think about it.

But analog cable is not optimized for impedence at all. Other things are important, like shielding, flex and microphonics are important too, so they are of very different design.

110 ohm digital cable is fine for line level audio, though.

Hope that helps, and possibly restores your faith in the helpful spirit of this community.
effitall
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3rd November 2010
Old 3rd November 2010
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There are many people that are using 110 ohm cable for studio wiring precisely for it's low-capacitance. I would step back from saying that some of these guys don't know what they're doing.

That said...Yes...I'm using a cable for an unintended application and having some unexpected issues with it. Just seemed like the microphonic issue when used as a mic cable would've been found and mentioned by someone before.

At any rate...As long as you're not moving the cables, they work fine.

James
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4th November 2010
Old 4th November 2010
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Quote:
Originally Posted by effitall View Post
There are many people that are using 110 ohm cable for studio wiring precisely for it's low-capacitance. I would step back from saying that some of these guys don't know what they're doing.
Well, if they are using 3080 looking for lower capacitance, they should look more carefully at the spces. 3080 specs at 14pf/foot between conductors, where 2534 quad is 1.2pf/foot, and the 2791 broadcast cable is 3.4pf/foot. All of the above count as low capacity cables, though, and all three types will perform quite well with any audio source and cable length up to hundreds of feet. However, reading the Mogami catalog on the 3080 page, I can see where the confusion may have begun. They make a point of the low C of 3080, and it's ability to transmit analog audio. But go read the specs of any of their mic cables too, which are better for mics, lower C, lower noise, but probably won't work well for digital in any length over a few feet.

The point of the digital cable is the impedance. It's part of the AES/EBU spec, 110 ohms, plus/minus 20%. Understand, that's the characteristic impedance of the cable, which has to match the driving source Z, and the termination load Z for highest quality transmission and lowest error. In digital signal transmission, impedance match of the source, cable, and termination is important, in audio it's absolutely not. Digital signals operate well into the RF band, where impedance differences cause the signal to be partially reflected back to the source. The effect is similar to a room mode. But with a digital signal, a reflection in a cable can introduce errors, which are not tolerable.

Audio. on the other hand, can work fine with lot of different cables. You just have to take into account the cable's design goals, and how they can work for you or against you. You may have found a negative to 110 ohm AES cable for use in a mic application. That doesn't make it bad, but everyone should read and understand cable specs before making the choice.

Get the Mogami Tech Catalog here:
http://www.mogamicable.com/pdf/Mogami_Tech_cat08.pdf

Jim
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